This invention relates generally to sewing machine drive apparatus and more particularly, but not by way of limitation, to an apparatus for enhancing traction between a pulley belt and a pulley forming part of a sewing machine main crankshaft drive assembly.
A conventional individual user type of sewing machine typically has a main crankshaft which is rotated by an electric motor. As the main crankshaft rotates, the sewing operation is performed.
The output shaft of the motor can be directly connected to the crankshaft, such as by a drive belt. In some applications, however, the power transmission occurs through a plurality of bets and one or more intermediate pulleys. One use of this type of intermediate subassembly would be for achieving speed reduction from the motor to the crankshaft.
Under light to normal operating loads, the traction between the belts and pulleys is normally sufficient to prevent the belts from jumping or slipping relative to the pulleys. Slotted pulleys and toothed belts have been used to provide mechanical engagement to avoid jumping o slipping.
Under heavy to maximum power loads, however, I have found that even the slotted pulley/toothed belt drive assembly exhibits jumping or slipping. This interrupts the smooth operation of the sewing machine and is certainly undesirable. Therefore, there is the need for providing a sewing machine drive assembly which exhibits no or reduced jumping or slipping even under maximum power loads.